1. Field of the Invention
The present invention relates generally to a head suspension of a disk drive incorporated in an information processing apparatus such as a personal computer, and particularly, to an electrode structure of a piezoelectric element used for the head suspension and a method of forming an electrode of the piezoelectric element.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing, and for use with such devices, needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
To meet the needs, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-50140 a head suspension for a disk drive, including a base plate, a connection plate having a hinge thinner than the base plate, a load beam provided with a flexure, and a piezoelectric actuator composed of a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for a precise positioning purpose, a voice coil motor and the piezoelectric actuator having two piezoelectric elements made of, for example, PZT (lead zirconate titanate). The piezoelectric actuator in the dual actuator system minutely moves a front end of the load beam in a widthwise direction (sway direction) of the head suspension.
Compared with a single actuator system employing only the voice coil motor, the dual actuator system employing the voice coil motor and piezoelectric actuator is capable of more precisely positioning a magnetic head attached to a front end of the head suspension.
In the head suspension employing the dual actuator system, the piezoelectric actuator is arranged in an opening formed in a piezoelectric element attaching part prepared on, for example, the base plate.
Each piezoelectric element in the piezoelectric actuator has upper and lower faces that are covered with electrodes. The electrodes of each piezoelectric element are connected to wiring through which power is supplied to the electrodes. The opening in the piezoelectric element attaching part of the head suspension has a support to support the bottom faces of the piezoelectric elements.
To effectively use a space, the piezoelectric elements are arranged in the opening close to the periphery of the opening, and therefore, the electrodes of the piezoelectric elements have a risk of contacting the attaching part. If the electrodes of the piezoelectric elements touch the attaching part, power supply to the piezoelectric elements will be hindered. To avoid this, the electrodes of the piezoelectric elements must electrically be insulated from the attaching part.
For the electric insulation, a related art employs an adhesive containing a filler made of insulative particles. The adhesive is applied so that the filler may interpose between the electrodes of the piezoelectric elements and the piezoelectric element attaching part of the head suspension.
The filler tends to unevenly disperse in the adhesive, to cause a short circuit between the electrodes of the piezoelectric elements and the attaching part at a location where the filler in the adhesive is sparse.
Such a risk of causing a short circuit between the electrodes of the piezoelectric elements and the attaching part increases when the piezoelectric elements are placed obliquely in the opening of the attaching part, or close to the edge of the opening.